The present invention relates to a turret type mounting table having a turret table with a plurality of work holding mechanisms and, more particularly, to a turret type mounting system having a mechanism for causing one holding mechanism to pick up a work such as an IC device from an external work feed device or the like at a fixed feed position on a rotational track and for causing one holding mechanism which holds the work to release the work at a fixed release position on the rotational track so as to mount the work.
More specifically, the present invention relates to a control device for a turret type mounting system which is essentially autonomous, is not adversely affected by a mounting order, types of works, the number of work holding mechanisms, and the like, and can sufficiently cope with changes in these factors.
A most advanced mounting system is indispensable to produce high-quality electronic/electric products in a large quantity. In order to insert standard parts such as ICs and resistors on a printed circuit board for electronic/electric products at normal positions, there are required an external feed device for feeding parts to this mounter and an external device for moving a printed circuit board since the mounter itself cannot feed parts or convey the printed circuit board. The device for moving the printed circuit board comprises, e.g., an X-Y table.
For example, Japanese Patent Laid-Open No. 61-136298 discloses a technique for performing vacuum suction and mounting of a work by arranging a plurality of suction heads in the edge of a rotary table and by rotating the rotary table. More specifically, Japanese Patent Laid-Open No. 61-136298 discloses an "automatic electronic parts mounting apparatus comprising an X-Y table for positioning a printed circuit board, a parts shelf disposed near the X-Y table and movable in a lateral direction, a rotatable turntable arranged between the parts shelf and the X-Y table, rotatable mounting heads mounted along the edge of the turntable at equal angular intervals, a plurality of mounting chuck mechanisms having different shapes and mounted at the distal ends of the mounting heads, and a plurality of cams arranged around the turntable,
wherein, of the plurality of mounting chuck mechanisms, one mounting chuck selected by driving the corresponding mounting head with a mounting chuck selection cam (of the plurality of cams) driven by electronic part type data is operated to cause a polarity selection cam driven by electronic part polarity direction data to change the direction of the selected mounting chute, an electronic part is chucked from the parts shelf; during rotation of the turntable, the mounting direction of the mounting head is selected by a mounting direction selection cam driven by the electronic part type data; and the electronic part is mounted on the printed circuit board on the X-Y table".
In the conventional example, however, since each head mechanism is fed by one pitch and then stopped, the following problems are presented.
For example, when 20 types of parts having ten shapes are to be mounted by 10 head mechanisms, the shapes of parts mounted in units of head mechanisms are generally different from each other. For this reason, a head mechanism which has completed parts mounting need not be stopped at pickup and insertion positions.
In a turret table which performs intermittent feeding in units of pitches, each head mechanism must be temporarily stopped at the pickup and insertion positions, and the number of unnecessary stops is increased. In a conventional turret type mounter, a tact period is prolonged, and workability is degraded.
In such a conventional turret type mounting system, a plurality of work holding mechanisms are rotated, and a position where a part is received from an external parts feed device is fixed. In addition, a position at which a part held by the turret table of the mounter is transferred to a printed circuit position, i.e., an insertion position (or release position), is also fixed due to the following reason. Since many types of parts are transferred from the parts feed device to the mounter, a large waiting space is inevitably required for the parts. In addition, the space above a printed circuit board subjected to parts insertion is large. For these reasons, a feed position for transferring parts from the parts feed device to the turret mounter and a release position at which the parts are inserted from the turret mounter to the printed circuit board are fixed to obtain higher efficiency. Therefore, transfer of necessary parts to the fixed feed position on the turret table is controlled by the parts feed device, and a shift of the insertion position on the printed circuit board to the fixed release position on the turret table is controlled by the X-Y table.
The parts feed device can move necessary parts to the fixed feed position at high speed since this movement is monotonous linear or rotational motion. No problem is posed even if the parts are fed at high speed because a large number of parts prior to mounting are properly held. Each part can be firmly gripped in the mounter prior to mounting, and the turret table is subjected to simple rotational motion. Therefore, high-speed rotational motion is suitable even in the mounter.
When the parts are continuously inserted from the mounter to the printed circuit board, it is difficult to move the X-Y table at high speed because although each part is simply inserted, the part must be clinched. For this reason, since the X-Y table must be moved at low speed, it is very important to find an order of movement of the X-Y table, i.e., an order of insertion of parts on the printed circuit board so as to move the table to all insertion positions of the parts within the shortest period of time at this low speed.
It is possible to find an optimal mounting order on each printed circuit beforehand.
The following problems are posed in this case.
(1) This optimal mounting order, i.e., the insertion order, must be maintained since it is optimal. When this order is maintained, the order of parts transferred from the mounter to the X-Y table must be the same as the insertion order.
(2) This optimal mounting order varies in products.
(3) In order to maintain optimal mounting orders for all products, an operation of the parts feed device, rotation of the turret table during transfer of parts from the parts feed device to the mounter, a pickup operation at a feed position on each holding mechanism, a release operation of the holding mechanism at the release position (insertion position), and the like must be taught in each optimal mounting order of each product type. It is, however, impossible to realize this control when the type of product varies.
When many types of products must be assembled, rotation of the turret table during transfer of parts from the parts feed device to the mounter, the pickup operation of each holding mechanism at the feed position, and the release operation of each holding mechanism at the release position (insertion position) are simple detailed operations in a conventional system.
The detailed operations are defined such that the turret table is stopped every rotation by a unit rotation amount and picks up a part, if any, at the feed position by a gripping operation of a holding mechanism, and the turret table sequentially releases parts at the release position (insertion position) so that the released parts are sequentially inserted. Assume that the next part to be transferred to the mounter in a given mounting order is a part A which cannot be gripped by a holding mechanism located at the pickup position. A dummy pickup operation (non-pickup operation) is performed by this holding mechanism, and the part A is picked up by the next holding mechanism.
That is, in order to maintain an optimal mounting order for all products, the following additional problems are posed by the conventional system:
(4) the turret table is stopped every time a holding mechanism (gripper head) comes to the feed position, and
(5) if a holding mechanism which comes to the feed position cannot grip a part located at the pickup position, this holding mechanism must perform a dummy pickup operation.
The operations (4) and (5) are obstacles which degrade total mounting efficiency in the conventional system.